Transportation of diagnostic specimens is a major concern for regulators. Diagnostic specimens are typically collected from a patient at a clinical site. However, due to economies of scale and other factors it is often not feasible to conduct the desired tests on the diagnostic specimen at the clinical site. Therefore, it may be necessary to transport the diagnostic specimen from the clinical site to a laboratory to conduct the required testing on the specimen.
Centralized laboratory testing facilities offer economies of scale. Laboratory testing equipment may be very expensive. Due to this significant expense, it may not be cost effective for each clinical site to have such equipment on location in order to analyze the limited number of diagnostic samples collected at that clinic. Centralized laboratory testing facilities, however, provide the ability to make a single investment in laboratory testing equipment with the ability to test samples from numerous clinics. The centralized laboratory facility may perform tests on samples collected at dozens or even more clinical sites.
In order to take advantage of centralized laboratory facilities and the corresponding economies of scale, diagnostic specimens must be transported from the clinical site to the centralized facility. The distance between the clinical site and centralized laboratory facility may be significant, requiring transport through local mail service or private courier service. In order to maintain the diagnostic specimen during transportation, the specimen must preferably be kept in an environment below xe2x88x9220xc2x0 C. This is done by packaging the specimen in a transport case with dry ice or liquid nitrogen to maintain the proper temperature. Even after the diagnostic specimen reaches the centralized laboratory facility it may need to be preserved for a prolonged period of time. Such preservation is accomplished by placing the specimen in a freezer requiring handling of the specimen packaging.
Problems arise with prior art methods of transporting diagnostic specimens. For example, the pressure vessel described in U.S. Pat. No. 5,509,255 requires a user to place the specimen into an inner specimen bag. The specimen bag is sealed by peeling off the tape, exposing an adhesive. Once the specimen bag is sealed, it is placed in a containment envelope. The containment envelope is sealed by removing the tape and exposing a pressure sensitive adhesive on a flap. The flap is folded towards the body of the containment envelope and sealed. However, pressure sensitive adhesives have been known to fail in temperatures below xe2x88x9220xc2x0 C. Such a failure of the pressure sensitive adhesive used to seal the containment envelope may expose those handling the bag during transport and storage to the specimen. It is possible that the diagnostic specimen contains an infectious substance, such as the HIV virus. Such exposure to diagnostic specimens during transport is both undesirable and unacceptable to regulators.
Certain embodiments of the present invention provide a cost effective and secure way to transport diagnostic specimens meeting all regulatory concerns. Diagnostic specimens may be placed in a flexible, air tight, liquid impervious inner bladder. The inner bladder comprises an access opening which may be sealed after placing the specimen inside the inner bladder. After it is sealed, the inner bladder may be placed inside the inner cavity of a containment envelope. The containment envelope is dimensionally stable at the maximum required pressures by industry regulations. The inner bladder in a fully expanded condition is larger than the cavity of the containment envelope such that pressure acts upon the inner bladder to place the inner bladder in compression with the interior cavity of the containment envelope in tension.
The containment envelope may comprise an elongated sheet having a first end and a second end. The first end of the containment envelope having a cavity extending from approximately slightly beyond the midpoint of the sheet to the distal portion of the first end of the containment envelope. The cavity may be sized to contain the inner bladder, maintaining it in tension as described. The second end of the containment envelope comprises a pocket extending from approximately the midpoint of the second end to the distal portion of the second end of the containment envelope.
The containment envelope is flexible, air permeable, and liquid permeable. After the specimen is placed in the cavity, the containment envelope may be folded so that the distal portion of the first end is adjacent to the distal portion of the second end, causing the portion of the cavity extending beyond the mid-point of the sheet to act as a seal. The distal portion of the first end may be placed in the pocket of the second end. The pocket is sized to create a friction fit when holding the first end.
Certain embodiments of the present invention operate in accordance with basic principles of science and can be made from low cost materials. A readily available sealable polymer plastic bag may be used for the inner bladder. These polymer plastic bags typically have little tensile strength, and in and of themselves can only withstand pressures of one or two pounds per square inch. However, when combined with the containment envelope, the tensile forces acting upon the polymer plastic bag are negligible. A polymer plastic bag in compression can take considerable compression force before a failure occurs. The containment envelope may be selected for its tensile strength. A containment envelope may be chosen to meet almost any pressure requirement. It is preferable that the containment envelope remain dimensionally stable at the maximum intended pressures. In other words, the containment envelope preferably must not expand like a balloon. For example, a containment envelope fabricated from woven stainless steel would have tremendous tensile strength. A preferred material that can be made into envelopes much in the same fashion as paper is a spun bonded olefin material sold by Dupont Canada Inc. under the trademark TYVEK. This material has a strip tensile strength of approximately 7.9 pounds per square inch. However, when formed into an envelope, which when expanded forms a generally elliptical shape, it is capable of withstanding between 15 and 20 pounds per square inch. TYVEK will meet pressure requirements set forth in most, if not all, international standards relating to the transportation of diagnostic specimens. For example, a five inch by 7 inch envelope made from TYVEK has a surface area of approximately seventy square inches. Fifteen pounds per square inch spread over a surface area of seventy square inches equates to a tensile strength able to resist over one thousand pounds of total force.
According to another aspect of the invention, there is provided a method of maintaining pressure containment on dangerous goods, such as diagnostic specimens. The method comprises placing dangerous goods into an interior cavity of a flexible, air tight, liquid impervious, inner bladder, and sealing an access opening into the interior cavity with a closure. Placing the inner bladder into an interior cavity of a flexible, air permeable, liquid permeable, containment envelope and closing the access opening to the cavity by folding the containment envelope and placing a first end of the containment envelope into a pocket located on a second end of the containment envelope. The containment envelope is preferably dimensionally stable at the maximum intended pressures. The cavity of the containment envelope is preferably smaller than the inner bladder in a fully expanded condition. Upon internal pressure acting upon the inner bladder the inner bladder is placed in compression with the interior cavity of the containment envelope while placing the containment envelope in tension.
Central repositories of biological and infectious substances have been a major growth industry recently. Tens of millions of specimens are on deposit with private and government agencies such as the CDC, USAMRID and others. These specimens represent a highly valuable resource for researchers and public health officials and scientists. Specimens need to be transported to, stored and dispensed from these sites. Typically the specimens are refrigerated at dry ice (xe2x88x9270 C.) or Liquid Nitrogen (xe2x88x92196 C.) temperatures. Certain embodiments of the present invention permit the transport of large quantities of these specimens to be transported in a convenient fashion. Package design is much easier due the size and flexibility of design of the inner containment. Typically a stainless steel open head drum was used resulting in a significant loss of interior volume of the packages for specimen containment.